Recently, a perpendicular magnetic recording system has been adopted in magnetic disk devices to increase their recording density and capacity. In the magnetic disk devices of this system, a recording head for perpendicular magnetic recording is opposed to the recording surface of a magnetic disk having a recording layer for perpendicular magnetic recording. With the recording head, data is recorded in a predetermined area of the magnetic disk by producing a perpendicular-direction magnetic field corresponding to the data to be recorded.
The recording head has a narrowed portion made of soft magnetism metal and includes a main magnetic pole that generates a magnetic field in the perpendicular direction, a return magnetic pole opposed to the main magnetic pole with a write gap therebetween to return magnetic flux from the main magnetic pole and form a magnetic circuit together with the main magnetic pole, and a coil that excites magnetic flux in the magnetic circuit formed by the main magnetic pole and the return magnetic pole to generate a recording magnetic field.
The recording head so configured also includes a high-frequency oscillator, for example a spin torque oscillator (STO) in the write gap to improve recording capability.
When the sampling frequency of recording data increases, the oscillation responsiveness of the high-frequency oscillator becomes insufficient and thus the high-frequency oscillator cannot be brought into a stable oscillation state within a 1-bit time length of the data. Consequently, when data of high sampling frequency is recorded, the oscillation of the high-frequency oscillator becomes unstable to interfere in an adjacent track and cause the adjacent track to deteriorate in quality.
Embodiments described herein aim to provide a magnetic disk device capable of suppressing deterioration of signal quality of an adjacent track due to the oscillation responsiveness of a high-frequency oscillator and improving the signal quality and the recording density.